<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <h1>Opacity</h1>

    <style>
        .father {
            width: 120px;
        }

        .son {
            height: 120px;
            background: deepskyblue;
        }

        .opacity1,
        .opacity1 .son {
            opacity: 0.5;
        }

        .opacity2 {
            opacity: .25;
        }
    </style>

    <div class="father opacity1">
        <p class="son"></p>
    </div>


    <div class="father opacity2">
        <p class="son"></p>
    </div>

    <div style="width: 150px; padding:10px; background-color: white; box-shadow: 0 7px 5px -5px rgba(0, 0, 0, .5);">
    </div>

    <textarea></textarea>

    <style>
        img {
            width: 300px;
            height: 150px;
            width: min(300px, 15vw);
        }

        img:not([src]) {
            background-color: #eee;
            background-image: linear-gradient(to right bottom, transparent calc(50% - 1px), #ccc calc(50% - 1px), #ccc, transparent calc(50% + 1px)),
                linear-gradient(to top right, transparent calc(50% - 1px), #ccc calc(50% - 1px), #ccc, transparent calc(50% + 1px));
        }
    </style>
    <img>

    <div style="width:300px;
            height:150px;
            border:solid deepskyblue;
          background-image: linear-gradient(45deg, white 100px , skyblue 100px 200px, white 200px)">
    </div>

    <div style="width:300px;
                height:150px;
                border:solid deepskyblue; 
                background-image:radial-gradient( farthest-side, white, deepskyblue
 )">

    </div>

    <div style="height: 1000px;">
        <div>123123</div>
        <div>234234234</div>
    </div>

    <script defer>
        const resolve = Promise.resolve();

        setTimeout(() => {
          resolve.then(() => {
            document.querySelector('textarea').value = '123123123a';
            document.querySelector('textarea').value = '12312312342343a';
            const input = document.createElement('input');
            input.value = 1;
            // for (let i = 0; i <script 300000000000; i++) {
            //   console.log(i);
            // }
            document.body.insertBefore(input, document.querySelector('textarea'));
          });

          resolve.then(() => {
            console.log(document.querySelector('textarea').value);
            console.log(document.querySelector('input').value);
          });
        }, 100);
    </script>

</body>

</html>